Video display screens typically provide a movable marker, referred to as a cursor, to provide a visible indication as to the current position of interest on the display screen. Traditionally, this function has been implemented by either the host system or the display logic circuitry. Lower cost, lower performance systems have used software to create and manage the cursor while more performance oriented systems have used more expensive logic circuits with the intention of minimizing system software overhead.
One example of a cursor circuit is disclosed in U.S. Pat. No. 4,555,772 entitled "Current Cursor Symbol Demarcation" assigned to the present assignee. This patent discloses a circuit for exclusively ORing selected cursor character data with corresponding image data in an image memory at the selected cursor position in the image.
U.S. Pat. No. 4,445,194 entitled "Multi-Directional Cursor Motion" assigned to the present assignee discloses a text processor that has a text storage buffer and a display control block both interconnected to an applications program and a display access method program wherein the processor and programs equate a contextual cursor address with a spatial cursor position to provide data to a refresh buffer which in turn provides display signals to visually present by means of the display screen a cursor at the identified position in text.
U.S. Pat. No. 4,093,996 entitled "Cursor for an On-The-Fly Digital Television Display Having an Intermediate Buffer and a Refresh Buffer" assigned to the present assignee discloses a cursor circuit that stores a coded representation of a cursor symbol in an intermediate buffer during a period of display where accessed by a conventional light pen.
U.S. Pat. No. 3,903,510 entitled "Scrolling Circuit for a Visual Display Apparatus" to Teletype Corporation discloses a circuit for addressing a storage memory to display data in a manner to combine a cursor row address counter with the memory address counter.